Method and apparatus for measuring and controlling fluid flow



J. F. HUTTO March 22, 1960 METHOD AND APPARATUS FOR MEASURING AND CONTROLLING FLUID FLOW Filed Jari. 9, 195s MEHOD AND APPARATUS FR lt/EASUMNG AND CONTRQLEJNG FiLUi'i) FLW John E. Hutto, Bartiesviiie, Okla., assigner to ifiriiiips Petroieum ornpany, a corporation or' Beiaware This invention relates to method and apparatus for measuring and controlling duid iiow in liuid distribution systems. ln accordance with one aspect, this invention relates to an improved method and/or apparatus arrangement for measuring and controlling fluid liow in a fluid distribution system wherein it is desired to maintain a constant predetermined total duid flow rate. In accordance with another aspect, this invention relates to an improved method and/or arrangement of apparatas for measuring and controlling the flow of reactants in a chemical Areaction process wherein it is desired to maintain a constant predetermined total flow of reactants passed to a place of utilization in said process. In accordance with another aspect, this invention relates to an improved method and/or arrangement of apparatus for measuring and controlling the flow of reactantsiin an ali-:ylation process wherein the ow rate of one ofv the reactants is controlled to obtaina predetermined constant ratio of one reactant to the total of the remaining reactants introduced into the reaction zone of said process.

In many fluid distribution systems comprising a plurality of duid flow streams that are introduced separately, for example, into a placek or zone of utilization, it is often desirable, if not essential, in some installations to maintain a predetermined constant total ow rate of the dow streams utilized in order to obtain a desired result. This is especially true, for example, in various chemical reaction processes wherein a plurality of reactants are introduced separately into the reaction zone of the process and wherein both fresh and recycled unreacted reactants are employed, and wherein it is desired to maintain the total ow of fresh and recycled reactant at some predetermined rate. One such process is the alkylation reaction wherein olefin and isoparain comprising both fresh and recycled unreacted isoparamn are employed as reactants, and wherein it is desired to maintain a constant total flow of fresh and recycled isoparain introduced into the reactor. Also in the alkylation process it is often desirable to maintain a fixed ratio of oleiin to total isoparaiiin reactant, which maybe made up of both fresh and recycled unreacted isoparafin passed to the reaction zone. Various methods and/or apparatus have either been utilized or suggested in the past for measuring uid ows and controlling same to produce a constant total ow; however, unfortunately many of these arrangements, for one reason or another, either have been to complicated for commercial utilization or they have been inaccurate and unreliable and consequently Were not corn-` mercially feasible.

Accordingly, an object of the present invention is to provide a relatively simple, reliable and eflicient combination of instruments for measuring various fiows in a fluid distribution system and controlling same to produce a total constant uid flow. Another object of this invention is to provide an improved method and/0r arrangement of instruments for maintaining a constant total ow of reactants in chemical reaction processes having ,separate'introduction of said reactantsainto the 192,5? atented Mar. 22, i966 by a more economical and efhcient operation of said process is'obtained. Other aspects, objects, as Well as the several advantages of this'invention are'apparent from the study of the disclosure, thedrawing, and the appended claims.

n accordance with abroad concept ofthe presentl invention, I provide'an improved method of measuring and controlling the liuid flow in a uid distribution system having aV plurality of fluid flow streams, and'wherein it is desired to maintain av constant total ow rate of said streams, comprising the steps of measuring the flow of each liow stream to obtain signals that areproportional to the square of iiow rate of each stream, passing said signals to square root extraction zones to obtain signals that are linear and directly proportional to the flow rate of each stream, totalizing said linear signals to obtain a `resultant linear signal that is directly proportional to the total flow rate of said streams, passing said resultant linear signal to a iiow controlling and recording zone and in response to changes in said resultant linear signal, adjusting the flow rate of one of said fluid streams to maintain said predetermined'total flow rate;

in accordance with a more specific concepty of l'the present invention, i provide an improved method of measuring and controlling the operation of a chemical process such as, for example, the alkylation of olens and isoparaiiins wherein-a pluralityof reactants, which may comprise fresh and unreacted recycled reactant, are separately introduced into a'place of utilization, such as the reactionvzone, and wherein it is desired to maintain a predetermined constant total reactant liow rate, comprising the steps of measuring the dow rate of each of said reactant streams to obtain a signal proportional to the square of the iiow rate of each stream, passing said signals to square root extraction zones to obtain linear signals that are directly proportional to the rate of flow of the individual streams, passing said linear signals to a totalizing zone to obtain an additive signal that is directly proportional to the total `iiow rate of said iluid reactant streams, passing said additive signal to a controlling and recording zone and employing said additive signal in-said controlling zone to adjust the liow rate of one of said streams in response to changes in said additive signal-so as to maintain said predetermined total rate.

In accordance with another concept of the presentl invention, I provide an improved arrangement of apparatus for measuring and controlling Huid dow in a fluid distribution system comprising in'combination; conduit means for conveying said tiuids; flow restriction means in said conduits; flow measuring and differential pressure transmitting means connected to said conduits to obtain-signals proportional to the square of ow rate in each of said conduits; mathematical calculating means comprising square root extraction means and totalizing means connected to obtain said signals and to convert said signals into a resultant linear signal that is directly proportional to the total flow rate in said conduits; control means connected to .obtainl said resultant linear signal; control valve means in one of said conduits connected to obtain impulses that are obtained from said control means responsive to changes in said resultant linear signal, `thereby maintaining a predetermined constant total ow rate of fluids in said system.

The various individual pieces of control equipment employed herein are of conventional well-known function and design. Consequently, only briefreference is made hereto their description.v Back pressure orflow control valves employed herein may be of any Well-known diaphragm type, such as pilot operated valves, pressure balance valves, or spring loaded valves. In any case, a change in the pressure which is being controlled produces an effect on the diaphragm valve so' as to cause it to either open or close. A back pressure control valve can be set to maintain any predetermined pressure. Consequently, a back pressure control valve set to maintain a given pressure tends to move to a more nearly open position at any pressure higher than the set pressure, is more nearly closed at any pressure lower than the set pressure, and -throttles when operating to maintain a pressure within a narrow range of the set pressure.` The liuid iiow responsive means employed is preferably an orifice meter, which may be connected to a control means, preferably a rate of ow control instrument. By iiow responsive means, it is meant any element or device which partially restricts the iiow and thus establishes a pressure diierential,'in a portion of the line, which is proportional to the square of the rate of iiow. Thus, an orifice plate, Venturi, etc., may be used in the practice of this invention. Lil-:ewise, the control means may include any instrument or device which is actuated by the flow responsive means to produce a control effect or signal which maytal-:e the form of a change in pressure or rate of flow of a iluid such as air, or hydraulic iluid, usually called the controlled fluid, or of an electric circuit which is energized or de-energized.

The control valve means or motor valve means referred to herein are preferably of the conventional diaphragm type and are controlled by liquid flow responsive means in combination with control instrument means, square root extraction means, totalizing means and a secondV controlling-recording means, so that when the flow rate of the controlled iiow stream as determined by the lion/ responsive means in said controlled stream decreases, for example, to below the predetermined minimum rate, a control eiect or signal will be produced by the iiow responsive means which will reset the control instrument which in turn will open or close the motor valve means as the case may be. For example, when the rate of flow of the controlled fluid stream decreasesto below the predetermined minimum, the signals produced by the flow responsive means in the controlled stream and in the other measured streams are passed to square root extraction means wherein signals directly proportional to the ilow rate of each stream are obtained, and these signals are then passed to a signal totalizing means wherein a single linear signal is obtained that is directly proportional to the total ow rate of the measured streams, and then this signal is passed to a second controlling-recording means, and in response to changes in this signal a bafe or dapper in the controlling means actuated by said signal will be brought into a more nearly closed position relative to an air nozzle, eg., which produces an increase in the co'ntrolled air pressure from the second control instrument to the rate of ow controller, thereby resetting the rate of liow controller, which in turn adjusts the controlled air pressure communicating with the diaphragm of the motor valve. Such a co'ntrol effect increases the pressure on the diaphragm and causes the motor valve to open or close depending upon the particular control combination employed.

In order to" further describe the apparatus and method of this invention reference is made to the attached drawing. The drawing diagrammatically represents an arrangement oi apparatus suitable for the practice of this invention. ln order that this invention may be more clearly understood a brief description of an alkylation process will be made. It is to' be understood that the iiow diagram is diagrammatic only and may be altered in many respects by those skilled in the art and yet remain within the scope of my invention.

Referring now to the drawing, isobutane fed by Way of conduit 11 and conduit 12, olefin comprising essentially butylene and propylene fed by way of conduit 10 and hydrofluoric acid catalyst by way of conduit 13 are commingled in alkylator or contacter 14, under alkylation conditions, thus obtaining an alkylation eiuent containing the desired alkylate product. The conditions of temperature, pressure and time, as well as the ratios of isobutane to olefin and of hydrocarbon to acid are well known in the art. Said conditions do not form a part of the present invention and can be supplied by one skilled in the art. The resulting effluent mixture from alkylator i4 is passed by way of conduit l5 to a settler 16 in which it is separated into anv acid phase and a hydrocarbon phase. Separated acid is recycled by way of conduit 17 to conduit 13 and then to alkylator 14, as described. The hydrocarbon phase from acid settler 16 is passed by way of conduit 1S into azeotrope column 19. The overhead product removed from column 19 by conduit 20 comprising light hydrocarbons and HF acid is condensed by cooler Zi'and introduced into accumulator 22 wherein the condensed materials are allowed to separate into an acidrich and hydrocarbon-rich phase.

The hydrocarbon-rich phase separated in accumulator 22 is reuxed and introduced into column 19 by conduit 23, and the acid-rich phase is removed from accumulator 22 and passed by way of conduit 24 and recycled to contactor 14 by way of conduit 13. A hydrocarbon kettle product is removed from column 19 by Way of conduit 25 and is passed through treater 26, such as a bauxite treater, to remove any traces of free hydrogen fluoride remaining in the hydrocarbon phase, and subsequently passed by conduit 27 and introduced into deisobutanizer column 23. From the botto'rn of deisobutanizer 28 there is withdrawn through conduit 30 a deisohutanized al-l kylate which is passed to debutanizer column 31, from which there is taken overhead normal butane through conduit 32 andy from the bottom of column 31 there is withdrawn through conduit 33 a debutanized alkylate product. This alkylate product can be passed, if desired, to a rerun treating zone and treated under conditions well known to those skilled in the art.

A hydrocarbon fraction comprising isobutane, propane, and gases lighter than propane is removed overhead from deisobutanizer 2S through conduit 29 and introduced into depropanizer 34, wherein propane and lighter gases are removed overhead through conduit 35. Isobutane is removed as kettle product from column 34 through conduit 36 and introduced into reboiler 37 wherein it is heated and part of the isobutane is recycled back to column 34 through conduit 38 and the remainder of the isobutane is removed from reboiler 37 by way of conduit 39 and recycled through conduit 12 and introduced into contactor 14, as previously described.

In accordance with the present invention, a uid iiow responsive means 40, usually an oriiice plate is located in line 39 to detect the rate of flow of recycled isobutane. Also, a Huid ow responsive means 46 similar to 4b is located in conduit 11 to detect the rate of flow of fresh isobutane'introduced into contacter 14. Control means 42 and 49, usually rate of flow controllers, communicate withow responsive means 40 and 46 and are located preferably near thereto. RFC-42 and 49 Y may have manual as well as an automatic set point. rl`he flow orifices 40 and 46 installed in the two isobutane streams produce signals, preferably pneumatic signals, proportional to` the square of dow rate of each of these streams by means of, for example, Foxboro d/p cells 41 and 43. ln the present embodiment, rate of flow controller 42. which controls the degree of opening of motor control valve 43 located in recycle isobutane line 39 is reset by a liquid level controller located on reboiler 37. Thus, a predetermined rate of ilow of isobutane is recycled to' contactor 14 through line 39, flow responsive means 4S, motor control valve means 43, and line 12. The pressure diierential signal produced across tiow orifice 40 is and `50 into square root extractor means 45a and b.

Square root extractor means 45a and b can be any suitable square root extraction instrument known in the art; however, I prefer to use the Storeberg force bridge such as disclosed in U.S. Patent 2,643,055, and also described in Minneapolis-Honeywell manual,lwhich can be conveniently used to-convert a pneumatic signal transmitted from a pressure diiierential flow transmitter into a linear output pneumatic signal that is directly/proportional to the flow rate of the measured iiuid ow stream.

Thus, by taking the square root of the signal the linearl signal obtained by extractor 45a is directly proportional to the dow rate of recycle isobutane in conduit 39 and is removed from square root extraction zone 45a through conduit 52 and introduced into totalizer 53. Likewise,

the linear pneumatic signal obtained that is directly proportional to the flow of fresh isobutane introduced through conduit El is passed from square root extraction zone @b into totalizer S3 by way of conduit 51.

Totalizer 53 can be any conventional instrument .capable of'adding linear signals, whether pneumatic or electronic in order to obtain a resultant linear signal that .is directly proportional to the total duid dow rates in conduits l1 and 3g. One such instrument that can be used as the totalizerv is aFoxboro model 56 computing relay which operates on a force balance principal. Other known instruments that Vwill perform arithmetical operations such as adding,M etc., and are capable of totalizing two or more linear signals to produce a single output linear signal can be employed in the practice of the present invention. The additive or, resultant linear pneumatic signal 0btained in totalizer 53 is passed by way of line 54 to controller-recorder means 55, having a manual set point therein corresponding to the total iow desired, wherein the additive signal is utiiized to reset rate of flow controller 49, which in'turn controls the flow of fresh isobutane passed through conduit 11 by regulatingmotor valve 47 thereby maintaining aV constant predetermined total dow of isobutane passed to contacter -i. Thus, the LLC on reboiler .37 provides thesignal which resets the set point for RFC-42 andcontroller S5 provides the signal which resets the set point for RFC-49 RFC-42 and 49 are conventional instruments such as shown in Foxboro Instrumentation Bulletin 453, pages 52 and 55, havim7 a pneumatic reset. l

rillus, in actual operatic-n a predetermined flow rate of isobutane is recycled through conduit 39 and regulated by motor valve d5 which in turn is held in a predetermined position by RG-d2- as determined by the set point on RFC-d2, which is reset as shown `in the drawin bv the LLC on reboiler 37. lf the liquid level in reboiler 37 drops, the isobutane dow in conduit 39 mustbe decreased. When the level drops in reboiler 37 the LLC resets RFC-42, which in turn pinches down motor valve 43. i

A pneumatic signal proportional to the square of dow in conduit Sii is transmitted by d/ p cell 41 to lsquareroot extractor 5a which in turn extracts the square root 'of l said signal to obtain a linear directly proportional to the flow rate in conduit 3:9 which is passed to totalizer means 53. Likewise, the constant dow of isobutane in conduit 11 is measured by flow responsive means 46 anda signal picked up by d/p .cell d, which transmitsfa pneumatic signalV also. proportional to the squareoftow in-,tcouduit ist, and the Vsquare rootrofsaid. signalisat-` Ltracted unitrdhand :the: resulting Alinear signal is -passed to-totalizer 53. Theftotal linear signal now obtained by totalizer'53, Which'fisfdirectly proportional to the-total uid `flow in conduits 11-and 39, is less than the preset .total rowof isobutane desired. Thus, in response to this .,change, controllerSS passes a pneumatic signal to RFC-.49which resetsthis instrument, which in turn opens motor valve 47 so as .to ,increase the ow of fresh isobutane in conduit 11. This increase in ow rate is then picked up by flow responsive means 46 and this signal have Vindicated in the above description of my inventionv that .I :prefer to use a combination of pneumatic instruments it should be realized that substantially the same vresults can be obtained by the use of electronic instruments, for example, or a combination of pneumatic and electronic instruments can be used, if desired. Pneumatic .signals can be conveniently converted into electronic signals rand vice versa by employing pneumaticelectronic transducers. The important concept of the present invention involves the arrangement of the pary ticular instruments disclosed in such a Way that the total ow rate `of severalrtluidow streams which are unmixed can be maintained at some predeterminedconstant total ow.

While the kcontrol apparatus is described along with the above described alkylationprocess'flow diagram it should be realized that more than two uidllow-streams can be controlled by the practice of this invention.` Further, the invention should not be construed as being limited specifically to HF alkylation` iiowcontrol since the method and apparatus can be applied tootherprocesses wherein a plurality of reactant streams are passed to a place of utilization and itis desiredtomaintain a predetermined total constant ow. Y

In connection with the above described alkylation process, the additive or resultant linear signal obtained in totalizer 53, Whichis directly proportional to the total how measured, could be used to reset olen feed flow by means of control valves..(not shown) so as to maintain a constant olefin-isobutane ratio.

One such control'arrangement can comprise, for example, a flow responsive elementin each ofthe feed streams passed to the alkylator, that is, fresh andrecycled isobutane and olefin feed streams, and a differentialY pressure transmitter connected to each of the flow responsive elements. A dow control valve such as a diaphragm motorvalve can be located in one ofthe isobutane streams and in the olefin stream, and each of the flow control valves is actuated by a flow controller connected to their respective differential pressure transmitters. Connected to each of the differential pressure transmitters is a square root extraction means to obtain a linear signal proportional to the flow rate in each of the individualtstreams, and the two signals obtained that are proportional tofgtheisobutane ow rates can be passed to a totalizing means to obtain a signal that is directly proportional to the total isobutane flow rate. .This Atotal linear signal in turn can be passed tothe flow controller connected to one or the isobutane'streams to maintain, a constant total dow rate of isobutane by adjusting the ow control valve in a particular isobutane stream. Also, the linearsignal obtainedrfrom the totalizingV means canalso be passed to a ratio controller whereinkthe ksignalobtained by the olefin square root extraction means is compared with the total flow rate of isobutane, and theresultant .signal'obtained from the ratio controller passed tothe thereby maintaining theldesired ratio-of: olefinwto isobutane. In such a system the total ow rate of fresh isobutane plus recycled isobutane is maintained constant by manipulating either one ofthe two streams. In addition, the ratio of fresh isobutane plus recycled isobutane to olefin is maintained constant by manipulating the olefin flow rate. Also, the iiow transmitter on one of the isobutane streams could have a controller and motor valve associated with it, manipulated, for example, by a liquid level controller.

In a less preferred embodiment of the above described ratio control system, the ow controller and its associated control valve employed in the above embodiment to regulate the flow of one of the isobutane streams could be eliminated, however, in such a control arrangement a total flow rate of fresh isobutane plus recycled isobutane is not maintained constant but rather both streams will vary at will. The ratio of fresh isobutane plus recycled isobutane to olefin can be maintained constant in such a control arrangement.

The utility of the instrumentation of the present invention can also be applied to other fluid distribution systems such as, for example, a gas-fired boiler or furnace wherein Yit is desired to feed a predetermined amount of gas to the burners, which are supplied by natural gas from one header and producer gas from another, and assuming that the natural gas is the cheaper gas to be used, the producer gas fiow vto the burners could be controlled in response to the measuring and controlling system of the present invention in order to maintain a predetermined total flow to the furnace from the two headers. The present invention may also be utilized in a return collection system for a plant cooling tower, for example, wherein measurement lof the ow in the final larger header might be impractical due to its large size, and by the practice of the present invention the smaller return streams could be measured which would produce a resultant signal representing the sum of the individual streams which then could be used to regulate make-up water added to the cooling tower.

My invention will be practiced primarily in connection with alkylation of isobutane with low-boiling olefins, such as butylenes and/or propylene or amylenes. The olefin feed may comprise a butane-butylene fraction or a butaneamylene or butylene-propylene fraction from a refinery. However, in many cases it will be possible to apply the features of my invention to the reaction of other low-boiling alkylatable compounds, especially the isoparaffins, particularly isopeutane, and low-boiling aromatics such as benzene and toluene, phenol, and cycloparains such as cyclohexane, and to apply the features of the invention when other alkylating reactants are employed, such as higher-boiling olefin hydrocarbons whether those are produced by polymerization or are produced by other means, such as cracking or dehydrogenation, and also when other alkylating reactants such as alkyl halides, alcohols and singilar'alkyl compounds are used. Y

As previously pointe'dout, the conditions of temperature, pressure, and time, as well as the ratios of isolmtanel vto olefin and of hydrocarbon to acid are well known in the art. However, the conditions in theallylator can be as follows: temperature 50-150 F.;lpr'essure sufficient to maintain liquid phase; average reaction time, of the order of about to l5 minutes, and rapid agitation to maintain intimate contact between acid and hydrocarbon phases.' The ratio of isobutane-to-alkylating agent or olefin will be about 6:1 to 10:1 by weight, acid-to-hydrocarbon ratio will beabout 2:1 by-weight. Any suitable liquid alkylation catalyst which is capable of eecting alkylation of the isobutane with the olefin under conditions herein described may be employed. speaking, I employ the liquid inorganic acids such as anhydrous hydrouoric acid and concentrated sulfuric acid.

The following is a specific example of operation ac- .'.cording to the present nventionas described above in con- .necuon wlth the attached drawing.

Generally 8 SPECIFIC EXAMPLE In a specific example employing a control arrangement described in connection with the drawing, alkylation reactor 14 is operated at 39 p.s.i.a and 78 F. The isototal alkylate. The olen, isobutane recycle, and fresh isobutane are introduced into reactor 14 at 90 F., after the streams are cooled to this temperature by indirect heat exchange with cooling water. Lower temperatures are not available due to cooling water limitations. Th recycle catalyst is introduced at 78 F,

Barrels per day 5,000 Composition, B/D:

Propylene 1,635

Propane 635 Butylene 1,660

Isobutane 835 n-Butane 235 Total olefin, B/D 3,295 Temperature, F 90 Fresh isobutane (11) Barrels per day 3,249 Composition, B/D:

Propane 67 IIsobutane 3,115

n-Butane 67 Total isobutane, B/ D 3,115 Temperature, F 90 Recycle isobutane (39) Y. Barrels per day k 29,600

Composition, B/D:

Propane 300 Isobutane 29,000

n-Butane 300 Total isobutane, B/D 29,000 Temperature, F 90 Catalyst (I3) Barrels per day 37,850 Wt. percent HF 94-.5 Temperature, F 78 Contactar (14) Pressure, p.s.i.a. 39 Temperature, F i 78 iC4/olefin mol -ratio 8.4:1 Cat/hydrocarbon vol. ratio 1:1 Alltylate (butano-free), B/D 5.-.... 5,600 Line {15),1B/Dey 36,204 Y Composition, B/D:

isobutane 29,000

Propane 1,002

n-Butane 602 Alkylate 5,600

tained, the improvement comprising the steps ofmcasur ing the flow ofi'saic fstreams`a'nd vrobtaining"signals 1.pro-

portional to thetsquare offiiowrrate ofeachstream, passing said 'signals to square rent extraction zones to obtain linear signals directly proportional to 'each Astream ;ow rate, passing said linear signals to a signal totalizing zone to -obtain a positive resultant variable linear signal Athat is directly proportional to the'total of the flow rates of said streams, passing ssdd resultant signal to YVa .ow controlling zone and in response to changes in vsaid :resultant linear signal employing said resultant signal to adjust the ow rate of one of said variable streams to maintain said predetermined total flow rate.

2. In a fluid distribution system comprising a plurality of variable iiuid flow streams that are separatelypassed unmixed to a place of utilization wherein a predetermined constant total ilow rate of said streams is maintained, the improvement comprising measuring the ow of each .stream to obtain pneumatic signals proportional to the square of each stream ow rate, passing saidsignals to square root extraction zones to obtain signals'that are linear and directly proportional -to each ow stream rate, totalizing said linear signals to obtain a positive resultant variable linear signal that is directly proportional to the total of the ow rates of said streams, passing said resultant signal to a flow controlling'zone, and responsive to changes in said resultant signal adjusting the iiow rate of one of said streams to maintain saidpredetermined total dow rate.

3. In a method of measuring the llow rate of each of a plurality of variable uid flow streamsin a huidl distribution system and controlling the flow of one '-of vsaid streams to maintain a predetermined constant ratio fof said one ow to the total of the remaining ows and to .maintain a predetermined constant total of said remaining hows, the improvement comprising measuring the ow rate of each said remaining `stream to obtain signals proportional to the square of ow of each said stream, passing said signals to square root extraction -zones to obtain linear signals directly proportional to the -low or" each said remaining stream,

passing said linear signals to a totalizing zone to obtain a positive resultant variable linear signal that is directly proportional to the total iiow rate of said remaining streams, passing said resultant linear signal to a ow controlling zone, employing said resultant signal to adiustrthe ow rate of oneA of said remaining streams so as to maintain a predeterminedconstanttotal iiow rate of said remaining streams, and further employing said resultant linear signal to adjust .the ow or said one stream so as to maintain a predetermined constant ratio of said one stream tosaid remaining streams.

4. In a reaction process having a plurality ol reactants introduced as separate unmixed fluid streams having variable ow rates into the reaction zone of said process wherein a predetermined total iiow rate of said streams ismaintaiued by controlling the ow rate of one of said streams, the improvement comprising measuring thellow Vof each stream to obtain pneumatic signals proportional to the square of the individual flow rates, passing said signals to square root extraction zones to obtain linear pneumatic signals that are directly proportional to said now rates, obtaining a resultant linear pneumatic signal that is directly proportional to the total dow rates of said streams by passing said linear signals to a totaiizing zone, passing said resultant linear pneumatic signal to a flow controlling zone, and ernployinor changes in said resultant linear signal to adjust the ilow rate of said one stream so as to maintain said predetermined total iiow rate.

5. in a rea tion process utilizing a plurality of reactants which are introduced as separate unmixed continuously llowing fluid streams having variable ow rates into a reaction zone of said process wherein an unreactedportion of one of said reactants is recovered and returned 4to "said reaction :zone 'for freuse,;and1the fiotalzzowooi Ysaid 'reactants lintroduced into-said reaction zoneuss'main- .tained at a predetermined value, .the improvement '.com-

prising measuringzthe ow rate of each of said'uid streams to obtain a signal proportional to the'squareiof the tlow ofy each of said streams, passing said signal-sito square root extraction :zones toobtain linearv signals that are directly. proportional to the ow rate of each ofiisaid streams, passing said linear signals to a totaliziug zone to obtain a resultant linear signal that is directly proportional to the total ow rate of said streams, passingsaid kresultant signal to'a controlling zone and adjustingfthe `flow rate of one of said streams in response to changes of said resultant signal to maintain the total .owirate of said streams at said predetermined value.

6. In an alkylation reaction process utilizing olen and fresh and unreacted recycled isoparain as reactants, said reactants vbeing introduced as separate, continuously `flowing variable uidstreams into the reaction zoneof individual isoparaiin streams, passing said linear .si-gnals to a totalizing zone to obtain an additive signal fdirectly proportional to the total ow of said isoparaln streams, passing said additive signal to a flow controlling zone employing said additive signal in saidflflow controlling zone to adjust the flow rate of one of said isoparain streams in response to changes in said additive signal -so asto maintain a predetermined-total isoparain ow, measuring the flow rate of said olen stream to obtain a signal proportional to the square of its ow, extracting thesquare root of said signal, comparing ythe signal thus obtained with said additive signal in a ratio control zone, and controlling said olen ow 'so vas'to maintain said predetermined ratio.

7. In an alkylation reaction process utilizing olefin and fresh and unreacted recycled isoparain as reactants, said reactants being introduced as separate continuously owing variable uid streams into the reaction zone of said process, trolled to maintain a predetermined constant ratio of olefin to the total of fresh and recycled isoparaiiin llows, the improvement comprising Vmeasuring the owfrate lof each of asid isoparain streams to obtain signals proportional to the square of the ilow rates of each of said isopara'n streams, passing said signals to square root Aextraction zones to 'obtain linear signals directly propor- Ysaid isoparafin streams, passing said additive lsignal to a controlling zone and employing said additive signal in said controlling zone to adjust the ow rate of `olefin in response to changes of said additive signal so as'to maintain said predetermined olen isoparain ratio.

8. In an alkylation reaction process'utilizing olelinf and fresh and unreacted isoparaihn as reactants, said reactants being introduced as separate variable fluid streams into the reactionY zone of said process, and whereinthe total flow of fresh and unreacted isoparadn introduced into said reaction zone is maintained at a predetermined value by controlling the ow of fresh isoparallin, the improvement comprising` measuring the ow rate of fresh and recycled isobutane flow streams to obtain signals proportional to the square of the flow of each stream,

'rectly' proportional to the rate of flow of fresh and `recycled isobutane, passing said linear pneumatic signals wherein the ow rate of olen is con- ;duits; dow measuring means connected to obtain signals proportional to the square of iiuid flow in each of said conduits; mathematical calculating means connected to obtain said signals and adapted to convert said signals :into linear signals that are directly proportional to the viiuid ow rates in each of said conduits; means connected to totalize said linear signals to obtain a resultant linear signal that is directly proportional to the total ilow rates of said streams; control means connected to obtain said resultant linear signal; and control valve means in one of said conduits connected so as to be adiusted by said control means in response to changes in said resultant linear Signal.

10. In combination with an alkylation process utiliz- I ing olefin and fresh and unused isoparatiin having variable flow rates as reactants, wherein the flow rate of said olefin stream is controlled to maintain a predeterv mined constant ratio of olefin to the total flow of isoparafiin, an improved uid iow measuring and control system comprising conduit means for flowing said reactants separately as unmixed streams to a reaction zone in said process; flow responsive means positioned in said conduits to detect the rate of ow of saidrreactants; iiow measuring means connected to obtain signals proportional to the square of uid ow in said conduits; square root extraction means connected to convert said signals into linear signals that are directly proportional to the fluid ow rate in said conduits; signal totalizing means connected to obtain an additive linear signal that is directly proportional to the total ilow in said isoparaftin-containing conduits; ratio control means actuated by said additive linear signal and by said linear signal from said olefin-containing conduit, said control means being -adapted to compare the signals passed to said means and obtain a resultant ratio signal; a motor control valve in said conduit conveying olefin connected to said ratio control means, said control means being adapted to adjust the tiow rate of said oletin by moving said valve means in response to changes in said ratiofsignal, thereby maintaining said predetermined ratio of isoparatin to olefin. t

1l. In combination with a fiuid tlow system comprising a plurality of coniined fluid fiow streams having vvariable ilow rates wherein it is desired to maintain a predetermined constant total iluid ow rate of said streams, an improved uid liow measuring control system comprising conduit means for conveying said uids separately as unmixed streams to a place of utilization; fiuid tiow responsive means in said conduits to detect the rate of tiow of fluids; motor valve means in one of said conduits; ow measuring means connected across said tiow responsive means in said conduits to obtain pneumatic signals proportional to the square of ow of each of said streams; square root extraction means for converting said signals into linear signals that are directly proportional to the ow rate of each stream; totalizing means connected to said square root extraction vmeans for adding said linear signals and to obtain a resultant linear signal that is directly proportional to the total ilow rate of said streams; ow control means operatively connected to said totalizing means to obtain said resultant linear signal, said flow control means being operatively connected to said motor valve means in said resultant signal so as to control the flow of fluid in said one conduit, thereby maintaining said predetermined total ow rate of said iluid streams.

12. In combination with a chemical reaction process having a plurality of reactants having variable flow rates introduced as separate unmixed iluid streams into the reaction zone of said process and wherein a predetermined total flow rate of said streams is maintained by controlling the ow rate of one of said streams, an improved uid tlow measuring and control system comprising conduit means for conveying said reactants to said reaction zone; flow responsive means in said cond uits to detect the rate of flow of fluid through said conduits; motor valve means to control the rate of flow of fluid in one of said conduits; flow-type control means actuated by said flow responsive means operatively connected to said motor valve means; flow measuring means connected to said ow responsive means to obtain pneumatic signals proportional to the square of ilow through said conduits; square root extraction means connected to obtain said pneumatic signals and adapted to convert .said pneumatic signals into linear pneumatic signals that are directly proportional to the ow rate in each conduit; totalizing means connected to obtain said pneumatic linear signals and adapted to add said signals `to obtain a resultant pneumatic linear signal proportional to the total flow rate in said conduits; control means operatively connected to said totalizing means to obtain said resultant pneumatic signal, said control means being operatively connected to said How-type control means and adapted to adjust said motor valve in response to changes in said resultant pneumatic signal so as to maintain said predetermined total flow rate.

13. In combination with an alkylation reaction process utilizing olefin and isoparaffin as reactants having variable flow rates and wherein the reactants are introduced as separate unmixed iluid streams into a reaction zone of said process and the total isoparaffin introduced into said reaction zone is maintained at a predetermined constant total fiow rate, said process having a first conduit means for unused isoparafn, second conduit means for fresh isoparain, and conduit'means for olefin reactant; flow responsive means to detect the rate of iiow of isoparatiin in said first and second conduits;

motor valve means positioned in said first and second conduits adapted to regulate the ow of isoparafiin through said first and second conduits; flow control means actuated by said flow responsive means operatively connected to said motor valve means; liow measuring means connected to said flow responsive means to obtain pneumatic signals proportionai to the square of tiow of said isoparaiin streams; square root extraction means connected to obtain said pneumatic signals and convert said signals into linear signals that are directly proportional to the flow rate of said isoparain streams; totalizing means connected to obtain said linear signals and convert said signals into a resultant linear signal proportional to the totai flow of said isoparain streams; control means connected to obtain said resultant signa?. and actuate said ow control means in said second conduit so as to reset the flow rate of said isoparafiin in response to changes in said resultant signal, and thereby maintaining said predetermined ow rate of said isoparain streams.

References Cited in the'le of this patent UNITED STATES PATENTS Sorteberg J une 23, 195 3 

